Water hammer type pumps are widely used in rural or suburban area where no electricity is available. An example of a water hammer type pump is provided in U.S. Pat. No. 4,073,604, as shown in FIG. 3. Water from a reservoir R, generally accumulated from a river, flows into the pump body B through a pipe P, raising the pressure in the pump body B. Suddenly, when the pressure within the pump body B is high enough, the valve V is closed. The pressure within the pump body B is further increased so as to push the piston head H move upward. Then, the water flows from the pump body B into the pressure tank T, from where it will be passed to the outlet pipe O by means of air pressure in the pressure tank T. As water is discharged from the pump body B to the pressure tank T, the pressure in the pump body B will be decreased, causing the piston head H to close and the valve V to open. Again, water flows from the reservoir R into the pump body B and begin another cycle. A flat valve F is provided between the outlet pipe O and the pressure tank T so as to prevent any reverse flow of water in order that water may be transferred to higher ground. An up and down movement of the piston stem S is utilized to drive a water drawing pump W in order to draw water from an under ground source to the reservoir R.
This pump tried to use the up and down motion of the piston stem S to draw all the water flowing through the valve V back to the reservoir R, this is similar to a perpetual motion which is impossible due to friction loss. Besides, the water used as a power source of the water hammer type pump is generally a river. Therefore, it is no need to worry about the supply of the water. The water drawing pump W appears to be redundant.